Many movie-goers in Calgary took a minute on their way into the theatre to think about the people who were killed during a midnight screening of screening of the new Batman movie ‘The Dark Knight Rises’ in Aurora, Colorado.

On Friday, a heavily-armed, masked gunman opened fire into a crowd at the theatre killing 12 people and injuring 59 others.

Aurora, Colorado is about 16 kilometres outside of Denver.

Police say the lone gunman released some sort of gas in the theatre before firing into the crowd.

The shooter was wearing a riot helmet, a bullet-proof vest and dressed from head to toe in black.

Ten people were killed on the scene and two others died in hospital.

Some of the injured were children, including a four-month-old baby who has been treated and released.

Police have identified the suspect as 24-year-old James Holmes.

According to a University of Colorado spokesperson, Holmes was studying neuroscience at the school until he dropped out of the PhD program about a month ago.

Police are not speculating on a motive and say Holmes was arrested without incident.

Cineplex, the operator of Canada’s largest theatre chain, responded to the tragedy and announced that part of the proceeds from Friday’s box office will go to a Red Cross Program that combats violence and abuse.

The theatre operators say they have stepped up security at cinemas across the country.

Investigators spent Friday scouring Holmes’ apartment and Century 16 Theatre, where the shooting unfolded.

A search of Holmes’ north Aurora apartment revealed sophisticated booby traps and explosives and police say it could take several days to dismantle.

Police say they will not release the names of the victims until all the families are notified.

Police released a written statement from Holmes' family Friday: "Our hearts go out to those who were involved in this tragedy and to the families and friends of those involved."

Meanwhile, many in the Denver suburb of 325,000 are left wondering what would provoke such an attack in the community.

(With files from The Associated Press and ctvnews.ca)